Grok: the Idea
It's been a month since I posted an entry in this ongoing series, but I got positive feedback and the story is not over yet, so here's a new entry! I hope you enjoy it!
Lost at CERN
In the summer of 2006 I went to the EuroPython conference, which that year was held in CERN, Switzerland. There was to be a Zope sprint ahead of the conference, so I came a few days earlier.
I got there in the evening. The next morning I tried to look for likely Python programmers. Normally this is not a difficult task: programming geeks tend to have a special look about them. But at CERN this doesn't work: many people at CERN look like they could be a programmer, and many of them of course are, but they were not there for EuroPython.
I got slightly lost in the complex, and was given directions by some gentlemen. They could've been janitors or Nobel prize winners, I will never know. CERN is a special place.
I finally concluded I had planned things a bit wrong, and had arrived at CERN one day earlier than everybody else. So I had a day to kill.
I remember the weather was gloriously sunny and warm. I was hanging out in the cafetaria for a while. I started thinking about my experiences with the new Zope, and its frustrations, and what it would take to turn it into a web framework without these frustrations. A web framework that I would like to use myself and would hopefully also be a bit less intimidating to beginners. Zope was starting to have a problem attracting new people -- the old Zope was out of date, and the new Zope was too intimidating.
The Idea of Grok
I decided to call this new framework Grok, as one has to give things a name. Grok is a term originally from Stranger in a Strange Land, a science fiction novel by Robert Heinlein, and is supposed to be a martian verb for "to understand/to become one with/to drink in". From there the word had made it into programming jargon.
Ruby on Rails had made popular the idea of "convention over configuration"; if you just use some conventions (naming, placing in modules, etc) for the entities in your system, the framework will know what they are without you having to explicitly and verbosely having to tell it. Since the new Zope had a problem with verbose configuration, I figured we could apply convention over configuration to make things more succinct.
In Grok you can use base classes (grok.View, grok.Model, etc) to signal what type of class you're definining, and the system will deduce from that how to register them with the Zope configuration system. Just base classes by themselves aren't enough though -- many configuration actions need parameters. We solved this with Grok directives.
For an example of a directive, You could associate a view with a model using the grok.context() directive. Grok directives are special calls you could make inside your class definition, like this:
class MyView(grok.View): grok.context(MyModel)
grok.context would magically apply to the class it is called in, in this case MyView, and set some information on it. These days we'd use a class decorator for this instead, but Python didn't have those yet then.
So far not much convention over configuration was going on. What I had done was found a way to integrate configuration information directly into Python classes so that you wouldn't have to maintain separate XML files anymore for configuration. Convention over configuration came in because you could leave out grok.context and it would then automatically associate the view with a model that happened to be defined in the same module.
It turned out later that convention over configuration in Grok was not as important as I had thought it was then. Some of the magic, even created very deliberately and layered over a worked-out configuration system, intimidated people and sometimes (though rarely) lead to unexpected behavior. The reduction of verbosity by doing configuration in Python near the code being configured was the main win; reducing that configuration further was less important.
When the other sprinters arrived at CERN, I explained some of these ideas to them and received some useful feedback. But it all remained just an idea.
After the Python conference, I was lucky enough to get to see the first web server (the web having been invented at CERN), and the Large Hadron Collider, which, they told us, was going to collide hadrons Real Soon Now.
This blog entry is a part of a series on Zope and my involvement with it. Previous. Next.
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